de Freitas Jorge M, Augusto-Pinto Luiz, Pimenta Juliana R, Bastos-Rodrigues Luciana, Gonçalves Vanessa F, Teixeira Santuza M R, Chiari Egler, Junqueira Angela C V, Fernandes Octavio, Macedo Andréa M, Machado Carlos Renato, Pena Sérgio D J
Departamento de Bioquímica e Imunologia, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil.
PLoS Pathog. 2006 Mar;2(3):e24. doi: 10.1371/journal.ppat.0020024. Epub 2006 Mar 31.
Acquisition of detailed knowledge of the structure and evolution of Trypanosoma cruzi populations is essential for control of Chagas disease. We profiled 75 strains of the parasite with five nuclear microsatellite loci, 24Salpha RNA genes, and sequence polymorphisms in the mitochondrial cytochrome oxidase subunit II gene. We also used sequences available in GenBank for the mitochondrial genes cytochrome B and NADH dehydrogenase subunit 1. A multidimensional scaling plot (MDS) based in microsatellite data divided the parasites into four clusters corresponding to T. cruzi I (MDS-cluster A), T. cruzi II (MDS-cluster C), a third group of T. cruzi strains (MDS-cluster B), and hybrid strains (MDS-cluster BH). The first two clusters matched respectively mitochondrial clades A and C, while the other two belonged to mitochondrial clade B. The 24Salpha rDNA and microsatellite profiling data were combined into multilocus genotypes that were analyzed by the haplotype reconstruction program PHASE. We identified 141 haplotypes that were clearly distributed into three haplogroups (X, Y, and Z). All strains belonging to T. cruzi I (MDS-cluster A) were Z/Z, the T. cruzi II strains (MDS-cluster C) were Y/Y, and those belonging to MDS-cluster B (unclassified T. cruzi) had X/X haplogroup genotypes. The strains grouped in the MDS-cluster BH were X/Y, confirming their hybrid character. Based on these results we propose the following minimal scenario for T. cruzi evolution. In a distant past there were at a minimum three ancestral lineages that we may call, respectively, T. cruzi I, T. cruzi II, and T. cruzi III. At least two hybridization events involving T. cruzi II and T. cruzi III produced evolutionarily viable progeny. In both events, the mitochondrial recipient (as identified by the mitochondrial clade of the hybrid strains) was T. cruzi II and the mitochondrial donor was T. cruzi III.
深入了解克氏锥虫种群的结构和进化对于控制恰加斯病至关重要。我们用五个核微卫星位点、24Sα RNA基因以及线粒体细胞色素氧化酶亚基II基因中的序列多态性对75株该寄生虫进行了分析。我们还利用了GenBank中可获得的线粒体基因细胞色素B和NADH脱氢酶亚基1的序列。基于微卫星数据的多维标度图（MDS）将这些寄生虫分为四个簇，分别对应克氏锥虫I（MDS簇A）、克氏锥虫II（MDS簇C）、第三组克氏锥虫菌株（MDS簇B）和杂交菌株（MDS簇BH）。前两个簇分别与线粒体进化枝A和C匹配，而另外两个属于线粒体进化枝B。将24Sα rDNA和微卫星分析数据合并为多位点基因型，并通过单倍型重建程序PHASE进行分析。我们鉴定出141种单倍型，它们明显分为三个单倍群（X、Y和Z）。所有属于克氏锥虫I（MDS簇A）的菌株均为Z/Z，克氏锥虫II菌株（MDS簇C）为Y/Y，而属于MDS簇B（未分类的克氏锥虫）的菌株具有X/X单倍群基因型。归入MDS簇BH的菌株为X/Y，证实了它们的杂交特性。基于这些结果，我们提出了以下克氏锥虫进化的最小情景。在遥远的过去，至少有三个祖先谱系，我们可分别称之为克氏锥虫I、克氏锥虫II和克氏锥虫III。至少有两次涉及克氏锥虫II和克氏锥虫III的杂交事件产生了具有进化活力的后代。在这两次事件中，线粒体受体（如通过杂交菌株的线粒体进化枝所确定）均为克氏锥虫II，线粒体供体为克氏锥虫III。
